Automatic safety shutter and motor control for picture-projecting machines



' 7 1,637,749 1927' c. F. HARRISON AUTOMATIC SAFETY SHUTTER AND MOTOR CONTROL FOR PICTURE PROJECTING MACHINES Filed Oct. 13, 1925 2 Sheets-Shet 1.

llmiL-L a a a v 1,637,749 Ana 2,1921 C,F.HARRBON AUTOMATIC SAFETY SHUTTER AND MOTOR CONTROL, FOR PICTURE RROJECTING MACHINES Filed Oct. 13, 1925 "2 Sheets-Sheet 2 Patented Aug. 2, 1927.

UNITED STATES 1,637,749 PATENT A OFFICE.

CHARLES FREDERICK HARRISON, OF LEVENSHULME, MANCHESTER, ENGLAND.

AUTOMATIC SAFE'I Y SHUTTER AND-MOTOR CONTROL FOR PICTURE-PROJECTING r MACHINES.

Application filed October 13, 1925, Serial No. 62,281, and in Great Britain April 30, 1925.

This invention relates to cinematograph or picture projecting machines, and has for its object to provide means whereby in the event of an abnormal variation in the tension of the film, say by breaking or becoming unduly slack or tight, the light of the lantern will be automatically intercepted, and the motor which the machine is operated stopped, thereby reducing the risk of fire to a minimum, as well as preventing further damage to the film.

According to the invention, use is madev of a shutter adapted to move across the path of the light, orbe held out of such path, meansbeing provided to normally retain the shutter in the retracted position. Use is also made of an electromagnet for releasing said shutter-retaining means, and of at least one switch in the magnet circuit for to completing such circuit, the switch being acted upon by the film to close the magnet circuit when the tension of the film varies from the normal, as aforesaid. On said shutter may be a further switch contacting with a stationary two-part bar alongside the shutter, the switch and one part of the bar being in the circuit ofthe motor which drives the machine, so that, with the open- J ing and closing of the shutter, the motor is started and stopped.

When there is no film passing through the machine, the switch in the magnet-circuit (or one of the switches when more than one) normally completes the circuit, but when a film is properly threaded through the machine, said switch is held by the film so as to break the magnet circuit. In this way the machine is prevented from running unless a film is first and properly inserted,v thereby affording additional safety in the use of the machine.

The l invention will be fully described with the aid of the .accompanying drawings, wherein a of cinematograph machine, with one example of the invention applied thereto, parts of the film reel boxes being shown broken away. I

Fig. '2 illustrates a diagram of the electrical connections of the improved safety mechanism. v

Fig. 3 illustrates to a larger scale, a front view of the shutter and magnet control and of the frame or casing supporting same, the

Fi 1 illustrates a general arrangement cover of the frame or casing being shown removed.

Fig. 4 illustrates a side view, and Fig. 5 a plan of a portion of the circuit control mechanism.

In Fig. 1, a is the lantern, b the projector, and 0 c the film reel boxes of the ordinary picture projecting machine. 03 is the frame or casing part of the improved safety appliances attached to the lantern on the side next the projector by means say of studs d and plates (P. In the plates d and in the back or rear wall of the casing d and also .in the cover of same, is formed a rectangular aperture, through which the light from the lantern normally passes. e is a shutter within the casing d sliding in vertical guides f. Such shutter. is normally held in a raised position above the aperture by means of the bolt or plunger 9 sliding in the horizontal guides h, the normal position of the plunger 9 being determined by a spring a and lever j. a k is an electro-magnet, and] the keeper of such magnet, said keeper, at its lower end, adjustably engaging the upper end of the lever j, and under the influence of the regulable spring m, normally being held clear of the magnet poles, as shown. Thespring i also serves to maintain contact between the keeper .Z and the lever 9'.

On the shutter e but insulated therefrom is a switch n in rubbing contact with a bar 0 g on but insulated from the frame d, Such .bar is in circuit with the electric motor used for driving the machine. Atits lower end the bar 0 is divided to provide an insulated gap, whereby on the shutter 6 being lowered and the switch n. passingthe gap, the motor circuit will be broken and the motor stopped, and similarly, on the shutter being raised and the switch passing from the lower to the upper bar, the motor will be restarted.

Adjacent to the usual upper feed roller ;0 aretwo pivoted metal plates or blades 7-, 1- normally resting against pins 8, s. The pivots of the blades and the pins 8, s are conveniently supported by the side wall of a housing or hood t, this latter being made of metal and lined with fibre or like insulating material 25 To the hood' t-"ile aP plied pairs of terminals to, u of the electric circuit of the magnet 71, against the points of which one or both of the blades 1', r

Flg. 4 by. a spring 4: and screw 0 so that the film in passing fronr the roller ;0 is guided into the hood t by the roller- 0 the film following the usual loop form be fore entering the gate, b-, see Fig. 4. On the open side of the hood is astay rod F for preventing the film leaving -t hood sideways.

Below the gate '6 and between the lower feed roller w and the lower film reel box c is a pivoted lever w, on one arm of which is mounted a roller m The other arm of the lever, in conjunction with terminals m constitutes a switch for completing or breakguide roller.

switch lever :17, loses ing the circuit of the magnet is. The lever 00 is mounted on the axis of the usual'bottom On its way from the bottom feed roller 10 to the lower film reel box a the film 9 passes below the roller w and over the guide roller y.

\Vith the film intact and running smooth-' ly at its normal tension, the plates r 1* lie clear of the terminals u, u and the lever w is held clear of the terminals 21 The film almost invariably breaks in the gate, but may also break at any point above or below the gate. Assuming the film to break in thergate, the broken end is held and the film ceases to pass through the gate, but by reason of the continued delivery of the film from the upper reel box 0 the loop of the film rapidly assumes large proportions, or in other words, balloons within the hood t, and contacting with one or both of the "plates 1- 1- moves it, or them, into contact with the respective terminals 11,, to thereby completing the circuit of the magnet k. Immediately the magnet is energized, the keeper Z operates the lever j to release'the safety shutter e, which instantly falls and closes the aperture in the frame (1.

Simultaneously with the film ballooning and operating the switch plates 1, r the the support of the film, and contacts with the terminals This also happens in the event of the film breaking at points other than in the gate, say above the loo or between the gate, andthe lower reel x.

The switches will operate in the same manner in the event of a film not breaking, but merely slackening.

Although undue tightening of the film is of rare occurrence, a further switch and terminals may be provided which will complete the magnet circuit when the film tightens to an unusual extent. Such-additiona-l switch will be arranged within the loop of the film, and may consist of a plate a slidable in slottedsupports and normally through the gate 6 its lowest point, the switch arm 11- passes the z by light gap in the bar 0 and breaks the circuit of I the motor used for driving the machine.

Immediately after the shutter is released by the lever it may break the magnet circuit and thus prevent waste of current or undue exhaustion of the battery. For such purpose the shutter may be furnished with a switch arm 2 and the casing d with terminals 2 with which the arm a engages when the shutter is fully raised to complete the magnet circuit, the circuit being broken on the arm leaving the terminals with the falling of the shutter.

To re-open the shutter after repairin or replacing the film, a handle 2 is provi ed, pivotally mounted in the frame d. In re placing or inserting a film, the operator first threads the film between therollers p and p and below roller 0 he then passes same then between the feed roller w and rollers w 10, then below roller :0 and over roller 3 and into the reel box 0. Unless the film is passed below the roller :2 the switch arm of the lever x will contact with the terminals 00 and prevent the restarting of the machine. In this way a safeguard is provided agains't inserting a repaired film or a new film without also at the same time resetting the safety devices.

To allow the o erator to see to repair or insert a film, t e fall of the shutter 0 may be used to switch. on a light and, for such purpose the shutter may be fitted along its lower edge with a pivoted switch bar e desi ned to engage a pair of terminals e fitted to a piece of insulating material carried by the casing (i, said terminals being in circuit with an electric lamp a. On the.

shutter being raised, the circuit of the lam is broken and the light extinguished. switch 2 may serve to switch on the light, independently of the machine.

With the safety shutter e additional to the ordinary shutter, this latter will be free to be operated in the usual way without interference from the safety shutter.

What I claim is 1. In picture" projecting machines embodying a lantern, a projector, and lower film feeding and guiding rollers, film reel boxes and an electric motor for driving the machine; in combination, a series of electric switches operated by the ballooning, tightening, slackening, or breaking of the film, terminals for said switches, means for sup orting some of said switches and terminals near the upper film feeding roller, another of said electric switches and terminals thereforbeing supported near to the lower film feeding roller, all the terminals being connected with an electro-ma'gnet and a gate, upper those switches near the upper feeding roller normally lying; clear of their terminals and the switch near the lower guiding roller nor mally lying in contact with its terminals. such last named switch being in the form of a lever and being axially mounted on" the axis of the lower guiding roller of the machine, and said lever having on one arm a further guiding roller, under which latter, after passing over the lower guiding roller, the film must pass and when correctly tensioned hold the switch clear of its terminals, a shutter, additional to the ordinary lantern shutter, a frame or casing with large a erture, and guides in said casing for the s utter to'slide in, said casing being separate from but secured to the lantern, and lying at right angles to the line of projectionvof the light :from the lantern, slidably supported by the casing and'in one position adapted to hold the shutter in the raised position and in another position release the shutter, the electro-magnet also being carried by the casing, a s ring-retracted keeper for said magnet, an a lever and spring for urging the plunger in one direction and at one end said lever abutting withof a shutter,

' from but secured to against the said magnet keeper, as set forth.

2. In picture projecting machines embodying a lantern, a projector, a gate, upper and lower film feeding and guiding rollers,

' film reel boxes and an electric. motor for driving the machine; the combination thereadditional to the ordinary lantern shutter, a frame or casing with large aperture, and guides in said casing for t e shutter to slide in, said casing being separate thelantern and lying to the line of projection of the light from the lantern, a rod or plunger slidably supported by the casing and in one position adapted to hold the shutter in the feeding roller, and a raised position and in another position release ;the shutter, an electro-magnet also carried by 'the casing, and a Tspring-retracted keeper for said magnet, a lever and spring for urging the plunger in one direction and at oneend said lever abutting against the said magnet keeper, aseries of electric switches and terminals and means for supporting same near the upper film further electric switch and terminals and means for supporting same near to the lower film feeding roller, all the terminals being in circuit-with the electro-ma et and those switches near-the upper fee ing roller normally 1 g clear of their terminals and the switc near the lower guiding roller normally lying in conits terminals such last named switchbeing in the form of a lever and being axially mounted on a rod or plunger of the lever, sai

the axis of the lower guiding roller of the having on one arm a further guiding roller, under which latter, after passing over the lower guiding roller, the film passes and when correctly tensioned, holds the switch clear of its terminals, a switch arm on the shutter, an interrupted bar on the casing in which the shutter slides, but insulated therefrom, over which theswitch arm may travel as the shutter moves up or down, said bar being in circuit withthe electric motor for driving the machine'and on the shutter falling and the switch arm passin from one part of the bar to the'other, t 1e circuit of the motor being broken and the motor stopped, as set forth.

machine, and said lever 3. In picture projecting machines and in a safety appliances therefor as claimed in claim one, a pair of pivoted metal blades or switches, adjacent the upper film feed roller, a hood for supporting the axes of said blades, or switches, terminals carried by said hood in circuit with the electro-magnet and with which the blades or switches are adapted to contact but which normally lie clear of said terminals, the arrangement being'such that the film on breaking and/0r unduly slackening or ballooning presses against one or other or both of the blades or switches and causes them to contact with the terminals and complete the circuit of the magnet, substantially as herein set forth.

4. In picture projecting machines and in safet appliances therefor, a series of electric switc es collectively operated by" either the ballooning, tightening, slackening or breaking of the film, an electro-magnet common to all said switches and electrically connected therewith and a shutter controlled by such electro-magnet for shuttingv off the light when the film balloons, tightens, ens or breaks, one of said switches comprlsin a lever on the axis of the bottom guide 'ro ler or sprocket wheel of the machine, a pair ofstationa terminals near'to one arm terminals being connected with the electro-magnet, and said lever having a roller orfurther sprocket wheel on the arm furthest from the "terminals,

slack;

whereby on a film being placed in the machine and I passed over one roller oriwheel and below,

the-other, the tension of the film serves to hold the lever clear of the terminals, while immediately the film breaks or slackens unduly, he lever makes contact with the terminals and completes the magnet circuit, the said circuit remaining comp ete'd until the lever is a in held clear of the terminals by a film, su antially as In testimony whereof I have signed my name to this specification. I

" p f C. F. HARRISON.

herein'iet fortln 

